Treatment of spinnerettes



Patented July 18, 1950 2,515,697 TREATMENT or SPINNERETTES ArthurCresswell, Stamford, Conn., assignor to American Cyanamid Company, NewYork, N. Y., a corporation oi. Maine N Drawing. Application April 5,1946, Serial No. 659,875

8 Claims. ,1 The present invention relates to the treatment ofspinnerettes employed in the production of synthetic or artificialfilaments and threads and more particularly to the treatment ofspinnerettes employed in the wet spinning" of such filaments and threadsto prevent plugging of the minute orifices contained in suchspinnerettes.

Synthetic or artificial threads and filaments are generally prepared byextrusion through very small orifices located in a multi-orificespinnerette. Such newly formed filaments are then frequently passed intoa spinning bath containing dissolved salts, acids or bases dependingupon the particular material extruded. This is the socalled wet spinningmethod in contrast to dry spinning methods where no spinning bath isemployed. Difiiculties with keeping the spinnerette orifices open areencountered in wet spinning both in starting up the spinning operationand in the course of such operation. These dimculties are occasioned bythe strong tendency of the newly formed filaments to adhere to the metalsurface of the spinnerette when the filaments or threads are preparedfrom protein materials as in the process disclosed in copendingapplication Serial No. 527,339, filed March 20, 1944. Particulardiificulty is experienced in starting up the spinning operation wherethe first portion of the extruded filaments must be pulled away from thespinnerette and attached toa spool. Also, if in the course of operationimpurities or air bubbles interrupt the continuity of the filamentextrusion, the extrudate tends to form a tenacious film over the surfaceof the spinnerette causing further filament rupture and eventuallyplugging a large number, if not all, of the orifices. In the extrusionof viscose rayon to form filaments, difliculty is likewise occasioned.by the adherence of minute particles which are insoluble in thespinning bath and which likewise tend to plug the spinnerette. Theviscose rayon filaments and threads are formed by extrusion of theplastic viscose into a spinning bath containing dilute H2804, ZnSO4 andNazSO4, and it is believed that the plugging difficulties experienced inthe operation of the spinnerette are due to the formation of very smallparticles of elemental sulfur which adhere to the surface of thespinnerette immediately adjacent to the orifices. The growth of theadhering deposit of insoluble particles results in encrustation andplugging of the orifices. In the formation of protein filaments andthreads such as those prepared from soy bean protein, casein, collagen,keratin, gelatin and the like, there is apparently no reaction with thematerial contained in the spinning bath, the filament formation beingsolely a process of coagulation. Thematerials contained in the spinningbath used in the formation of protein filaments are the necessaryacid-or base required to maintain the pH at the desired value,formaldehyde, and such salts as A12(SO4)3, Na2SO4 (NH4) 2304 and thelike.

It has been discovered that the above detailed difficulties withplugging of the spinnerette in the production of artificial threads andfilaments can be substantially eliminated by applying a film of asilicone to the surface of the spinnerette. Covering the metal surfaceof the spinnerette with a film of silicone apparently results in substantial elimination of any tendency for the newly formed filaments orother materials to adhere to the surface of the spinnerette.Accordingly, in starting up the spinning operation the filaments aremore easily pulled away from the spinnerette for attachment to thewinding spool and any interruption in the filament extrusion in thecourse of production does not result in plugging, such broken filamentsbeing carried along with the large number of other filaments emergingfrom the spinnerette. Likewise, the tendency to encrustation in theproduction of viscose rayon filaments and threads is considerablyreduced, the minute impurities formed in the course of the reactionwhich results in the rayon filament having a considerably reducedtendency to adhere to the surface of the spinnerette.

The silicones employed in the present invention have been described inU. S. Patents Nos. 2,258,219-2,258,222, inclusive, as linear polymers oisilicon in which the following is believed to be the structural unitwhere the Rs may be hydrogen and the same or different aliphatic or arylradicals. The silicon and oxygen atoms are directly connected,alternating in the chain of which the polymer is composed.

The silicones are employed in solution in a volatile organic solventsuch as benzene, toluene, butylacetate, ethylacetate, ether, acetone andthe like. The solution may contain from 0.01% to 25% of silicone,preferably 5%, and is applied to the spinnerette by any suitable meanssuch as spraying, or brushing or simply by dipping the spinnerette intothe silicone solution. The solvent is evaporated at a suitabletemperature,

preferably below 100 C. In order to insure keeping the orifices of thespirmerette open it is advisable to blow or draw air or other gasthrough the orifices of the spinnerette while the solvent is beingevaporated. Preferably the air is drawn through the orifices from theoutside of the spinnerette to the inside to draw the silicone throughsaid orifices and coat the orifice walls and the inside surface of thespinnerette immediately adjacent to said orifices. While this results ina film suitable for use in wet spinning filaments a more adherent filmis obtained by curing" the film of silicone by suitable heat treatment.The heat treatment required depends upon the particular siliconeinvolved, but generally the film is heated at 150-250 C. for V -6 hours,the longer periods of time being required at the lower temperatures.However, periods as long as 24 hours have been required in some casesespecially where temperatures below 150 C. must be employed. It isbelieved that the curing operation results in the formation ofcross-linkages between the respective chains of the silicone linearpolymer.

A spinnerette treated according to the process of the present inventionmay be employed in the extrusion of a dilute organic acid solution ofcollagen containing from 5-15% of the latter, said spinnerette beingimmersed in a spin bath containing at least 35% ammonium sulfate andmaintained at a pH of 7.8 without initial sticking and withsubstantially no stoppage during operation.

The following is a description of the preferred procedure of the presentinvention: A 5% solution of a silicone in toluene is prepared and thespinnerette to be treated is dipped into the silicone solution. Thesolvent isremoved by evaporation at a temperature not exceeding 100 C.while drawing air through the spinnerette orifices from the outside tothe inside. After evaporation of the toluene the spinnerette is heatedat 150-250 C. for a period sufficient to cure the silicone film andrender it more strongly adherent and resinous. In the case of methylsilicones heating at 225 C. for 1-2 hours or at 200 C.

for 3-6 hours is suflicient to effect curing while the phenyl siliconesheating at 250 C. for 1-3 hours or at 225 C. for 6-15 hours issufflcient while in the case of methyl phenyl silicone heat ing at 175C. for about 25 minutes is all that is required to cure the film.Examples of silicones which may be applied in this manner are methylphenyl silicone, ethyl phenyl silicone, ethyl chlorophenyl silicone,diphenyl silicone, diethyl silicone, dibutyl silicone, dipropylsilicone, propyl phenyl silicone and the like.

To facilitate further starting up of the spinning operation and pullingaway the first portion of the extrudate for attachment to a windingspool, a thin film of an amine of the type disclosed in copendingapplication Serial No. 580,081, now Patent Number 2,475,128, filedFebruary 27, 1945, may be applied to the spinnerette over the siliconefilm. Such amines are of the formula where R1 is a member of the groupconsisting of hydrogen, alkyl, aryl and acyl radicals and R2 may be anyaliphatic radical containing more than eleven carbon atoms. Such aminesform films only slightly adherent, wearing ofi' readily as the spinningoperation proceeds and, therefore, must be renewed almost every time onthe occa- 4 sion of starting up the spinning operation. Such a film ofamine is preferably applied to the more strongly adherent siliconefilament resulting from the aforementioned curing process because of themanipulative difiiculties involved in applying the film of amine withoutdisrupting the continuity of the film of silicone which has been appliedsimply by evaporation.

What is claimed is:

1. A metallic spinnerette carrying an adherent cured film of a siliconeconsisting of a linear polymer of the structural unit in which R is amember of the group consisting of hydrogen, aliphatic, and arylradicals, the R's being the same or different.

2. A metallic spinnerette carrying an adherent cured film of a methylsilicone consisting of a linear polymer of the structural unit in whichR is a member of the group consisting of hydrogen, aliphatic, and arylradicals, the HS being the same or different.

3. A metallic spinnerette carrying an adherent cured film of a phenylsilicone consisting of a linear polymer of the structural unit in whichR is a member of the group consisting of hydrogen, aliphatic, and arylradicals, the R's being the same or different.

4. A metallic spinnerette carrying an adherent cured film of a siliconeconsisting of a linear polymer of the structural unit in which R is amember of the group consisting of hydrogen, aliphatic, and arylradicals, the Rs being the same or different upon which is superimposeda film of an amine of the following formula RAPE where R1 is a member ofthe group consisting of hydrogen, alkyl, aryl and acyl radicals and R2may be any aliphatic radical containing more than eleven carbon atoms.

5. In a wet spinning process comprising extruding a suitable liquifiedmaterial through a spinnerette into a spinning bath wherein saidmaterial is solidified into threads, filaments and the like, theimprovement comprising using a spinnerette carrying an adherent curedfilm of a silicone consisting of a linear polymer of the structural unitR [has] in which R is a member of the group consisting of hydrogen,aliphatic, and aryl radicals, the R's being the same or difierent.

6. In a wet spinning process comprising extruding a suitable liquifledmaterial through a spinnerette into a spinning'bath wherein saidmaterial is solidified into threads, filaments and the like, theimprovement comprising using a spinnerette carrying an adherent curedfilm of a methyl silicone consisting of a linear polymer oi! thestructural unit in which R is a member of the group consisting ofhydrogen, aliphatic, and aryl radicals, the R's being the same ordiflerent.

7. In a wet spinning process comprising extruding a suitable liquifiedmaterial through a spinnerette into a spinning bath wherein saidmaterial is solidified into threads, filaments and the like, theimprovement comprising using a spinnerette carrying an adherent curedfilm of a phenyl silicone consisting of a linear polymer of thestructural unit in which R is a member of the group consisting ofhydrogen, aliphatic, and aryl radicals, the It's being the same ordifferent.

8. In a wet spinning process comprising extruding a suitable liquifiedmaterial through a spinnerette into a spinning bath wherein saidmaterial is solidified into threads, filaments 'and thelike, theimprovement comprising using a spinnerette carrying an adherent curedfilm of a silicone consisting of a linear polymer or the structural unitREFERENCES CITED The following references are of record in the file oi.this patent:

UNITED STATES PATENTS Number Name Date 2,100,581 weeldenburg Nov. 30,1937 2,294,154 Barthelemy et al. Aug. 25, 1942 2,310,207 Bley Feb. 9,1943 2,333,206 Sloan Nov. 2, 1943 2,356,542 Sloan Aug. 22, 19442,386,259 Norton ..l.'.. Oct. 9, 1945 2,386,466 Hyde Oct. 9, 19452,405,988 Barry Aug. 20, 1946

8. IN A WET SPINNING PROCESS COMPRISING EXTRUDING A SUITABLE LIQUIFIEDMATERIAL THROUGH A SPINNERETTE INTO A SPINNING BATH WHEREIN SAIDMATERIAL IS SOLIDIFIED INTO THREADS, FILAMENTS AND THE LIKE, THEIMPROVEMENT COMPRISING USING A SPINNERETTE CARRYING AN ADHERENT CUREDFILM OF A SILICONE CONSISTING OF A LINEAR POLYMER OF THE STRUCTURAL UNIT